Role of the Intracarotid Amobarbital‐Pentylenetetrazol EEG Test in the Diagnosis and Surgical Treatment of Patients with Complex Seizure Problems

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Abstract
The results of surgical treatment of intractable epilepsy seizures in a group of patients investigated with the intracarotid amobarbital-pentylenetetrazol EEG test were analyzed. This diagnostic test, originally designed to distinguish a mechanism of primary from that of secondary bilateral synchrony in the EEG, was also used in a small group of patients with independent bilateral temporal epileptiform spiking. The test was carried out in 99 patients of which 34 were operated on. Not all the operated patients fulfilled the test criteria for secondary bilateral synchrony. The follow-up studies demonstrated that when the test results pointed to a lateralized predominance of the epileptic mechanisms, regardless of whether or not the test pattern fulfilled the criteria of secondary bilateral synchrony, a circumscribed excision of epileptogenic brain tissue under cortical EEG control could be expected to produce a reasonably satisfactory reduction of seizure incidence in about half the patients. Asymmetries of the arterial supply to the cerebral hemispheres must be taken into account. The validity of the test results was greatly impaired when the carotid artery on the side, presumed to be the more epileptogenic on the basis of the test results, supplied not only the ipsilateral but also part of the contralateral hemisphere. The lack of any important difference in the follow-up results between patients with a test pattern of secondary bilateral synchrony and those in which the test results indicated a diffuse or multifocal epileptogenic condition with a lateralized predominance suggested that the classical concept of secondary bilateral synchrony must be revised. This condition probably represents only a particular variety of generalized epilepsy (often caused by widespread brain lesions) in which a localized area of cortex has assumed a dominant pacemaker role in the precipitation of generalized epileptic discharges. There is probably no sharp dividing line between this form of generalized epilepsy with secondary bilateral synchrony and others in which a wide range of asymmetry of the epileptogenic process can be demonstrated.